Seeing Central African forests through their largest trees
Bastin, J.F. ; Barbier, N. ; Réjou-Méchain, M. ; Fayolle, A. ; Gourlet-Fleury, S. ; Maniatis, D. ; Haulleville, T. De; Baya, F. ; Beeckman, H. ; Beina, D. ; Couteron, P. ; Chuyong, G. ; Dauby, G. ; Doucet, J.L. ; Droissart, V. ; Dufrêne, M. ; Ewango, C.E.N. ; Gillet, F. ; Gonmadje, C.H. ; Hart, T. ; Kavali, T. ; Kenfack, D. ; Libalah, M. ; Malhi, Y. ; Makana, J.R. ; Pélissier, R. ; Ploton, P. ; Serckx, S. ; Sonké, B. ; Stevart, T. ; Thomas, D.W. ; Cannière, C. De; Bogaert, J. - \ 2015
Scientific Reports 5 (2015). - ISSN 2045-2322 - 8 p.
tropical forest - biomass - size - distributions - diversity - dynamics
Large tropical trees and a few dominant species were recently identified as the main structuring elements of tropical forests. However, such result did not translate yet into quantitative approaches which are essential to understand, predict and monitor forest functions and composition over large, often poorly accessible territories. Here we show that the above-ground biomass (AGB) of the whole forest can be predicted from a few large trees and that the relationship is proved strikingly stable in 175 1-ha plots investigated across 8 sites spanning Central Africa. We designed a generic model predicting AGB with an error of 14% when based on only 5% of the stems, which points to universality in forest structural properties. For the first time in Africa, we identified some dominant species that disproportionally contribute to forest AGB with 1.5% of recorded species accounting for over 50% of the stock of AGB. Consequently, focusing on large trees and dominant species provides precise information on the whole forest stand. This offers new perspectives for understanding the functioning of tropical forests and opens new doors for the development of innovative monitoring strategies.
Height-diameter allometry of tropical forest trees
Feldpausch, T.R. ; Banin, L. ; Phillips, O.L. ; Baker, T.R. ; Lewis, S.L. ; Quesada, C.A. ; Affum-Baffoe, K. ; Arets, E.J.M.M. ; Berry, N.J. ; Bird, M. ; Brondizio, E.S. ; Camargo, P. de; Chave, J. ; Djagbletey, G. ; Domingues, T.F. ; Drescher, M. ; Fearnside, P.M. ; Franca, M.B. ; Fyllas, N.M. ; Lopez-Gonzalez, G. ; Hladik, A. ; Higuchi, N. ; Hunter, M.O. ; Iida, Y. ; Salim, K.A. ; Kassim, A.R. ; Keller, M. ; Kemp, J. ; King, D.A. ; Lovett, J.C. ; Marimon, B.S. ; Marimon-Junior, B.H. ; Lenza, E. ; Marshall, A.R. ; Metcalfe, D.J. ; Mitchard, E.T.A. ; Moran, E.F. ; Nelson, B.W. ; Nilus, R. ; Nogueira, E.M. ; Palace, M. ; Patino, S. ; Peh, K.S.H. ; Raventos, M.T. ; Reitsma, J.M. ; Saiz, G. ; Schrodt, F. ; Sonké, B. ; Taedoumg, H.E. ; Tan, S. ; White, L. ; Wöll, H. ; Lloyd, J. - \ 2011
Biogeosciences 8 (2011). - ISSN 1726-4170 - p. 1081 - 1106.
amazon rain-forest - elfin cloud forest - leaf gas-exchange - montane forest - aboveground biomass - spatial-patterns - hydraulic architecture - altitudinal transect - environmental-change - neotropical forest
Tropical tree height-diameter (H:D) relationships may vary by forest type and region making large-scale estimates of above-ground biomass subject to bias if they ignore these differences in stem allometry. We have therefore developed a new global tropical forest database consisting of 39 955 concurrent H and D measurements encompassing 283 sites in 22 tropical countries. Utilising this database, our objectives were: 1. to determine if H:D relationships differ by geographic region and forest type (wet to dry forests, including zones of tension where forest and savanna overlap). 2. to ascertain if the H:D relationship is modulated by climate and/or forest structural characteristics (e.g. stand-level basal area, A). 3. to develop H:D allometric equations and evaluate biases to reduce error in future local-to-global estimates of tropical forest biomass. Annual precipitation coefficient of variation (PV), dry season length (SD), and mean annual air temperature (TA) emerged as key drivers of variation in H:D relationships at the pantropical and region scales. Vegetation structure also played a role with trees in forests of a high A being, on average, taller at any given D. After the effects of environment and forest structure are taken into account, two main regional groups can be identified. Forests in Asia, Africa and the Guyana Shield all have, on average, similar H:D relationships, but with trees in the forests of much of the Amazon Basin and tropical Australia typically being shorter at any given D than their counterparts elsewhere. The region-environment-structure model with the lowest Akaike's information criterion and lowest deviation estimated stand-level H across all plots to within amedian -2.7 to 0.9% of the true value. Some of the plot-to-plot variability in H:D relationships not accounted for by this model could be attributed to variations in soil physical conditions. Other things being equal, trees tend to be more slender in the absence of soil physical constraints, especially at smaller D. Pantropical and continental-level models provided less robust estimates of H, especially when the roles of climate and stand structure in modulating H:D allometry were not simultaneously taken into account.
Increasing carbon storage in intact African tropical forests
Lewis, S.L. ; Lopez-Gonzalez, G. ; Sonké, B. ; Affum-Baffoe, K. ; Ewango, C.E.N. - \ 2009
Nature 457 (2009). - ISSN 0028-0836 - p. 1003 - 1006.
long-term plots - atmospheric transport - rain-forest - co2 - climate - biomass - disturbances - dioxide - impacts - balance
The response of terrestrial vegetation to a globally changing environment is central to predictions of future levels of atmospheric carbon dioxide1, 2. The role of tropical forests is critical because they are carbon-dense and highly productive3, 4. Inventory plots across Amazonia show that old-growth forests have increased in carbon storage over recent decades5, 6, 7, but the response of one-third of the world's tropical forests in Africa8 is largely unknown owing to an absence of spatially extensive observation networks9, 10. Here we report data from a ten-country network of long-term monitoring plots in African tropical forests. We find that across 79 plots (163 ha) above-ground carbon storage in live trees increased by 0.63 Mg C ha-1 yr-1 between 1968 and 2007 (95% confidence interval (CI), 0.22¿0.94; mean interval, 1987¿96). Extrapolation to unmeasured forest components (live roots, small trees, necromass) and scaling to the continent implies a total increase in carbon storage in African tropical forest trees of 0.34 Pg C yr-1 (CI, 0.15¿0.43). These reported changes in carbon storage are similar to those reported for Amazonian forests per unit area6, 7, providing evidence that increasing carbon storage in old-growth forests is a pan-tropical phenomenon. Indeed, combining all standardized inventory data from this study and from tropical America and Asia5, 6, 11 together yields a comparable figure of 0.49 Mg C ha-1 yr-1 (n = 156; 562 ha; CI, 0.29¿0.66; mean interval, 1987¿97). This indicates a carbon sink of 1.3 Pg C yr-1 (CI, 0.8¿1.6) across all tropical forests during recent decades. Taxon-specific analyses of African inventory and other data12 suggest that widespread changes in resource availability, such as increasing atmospheric carbon dioxide concentrations, may be the cause of the increase in carbon stocks13, as some theory14 and models2, 10, 15 predict.
The odd man out? Might climate explain the lower tree alpha-diversity of African rain forests relative to Amazonian rain forests?
Parmentier, I. ; Malhi, Y. ; Senterre, B. ; Whittaker, R.J. ; Alonso, A. ; Balinga, M.P.B. ; Bakayoko, A. ; Bongers, F.J.J.M. ; Chatelain, C. ; Comiskey, J. ; Cortay, R. ; Djuikouo Kamdem, M.N. ; Doucet, J.L. ; Gauier, L. ; Hawthorne, W.D. ; Issembe, Y.A. ; Kouamé, F.N. ; Kouka, L. ; Leal, M.E. ; Lejoly, J. ; Lewis, S.L. ; Newbery, D. ; Nusbaumer, L. ; Parren, M.P.E. ; Peh, K.S.H. ; Phillips, O.L. ; Sheil, D. ; Sonké, B. ; Sosef, M.S.M. ; Sunderland, T. ; Stropp, J. ; Steege, H. ter; Swaine, M. ; Tchouto, P. ; Gemerden, B.S. van; Valkenburg, J. van; Wöll, H. - \ 2007
Journal of Ecology 95 (2007)5. - ISSN 0022-0477 - p. 1058 - 1071.
plant-species richness - tropical forests - geographical ecology - equatorial africa - red herrings - dynamics - patterns - scale - disturbance - vegetation
1. Comparative analyses of diversity variation among and between regions allow testing of alternative explanatory models and ideas. Here, we explore the relationships between the tree alpha-diversity of small rain forest plots in Africa and in Amazonia and climatic variables, to test the explanatory power of climate and the consistency of relationships between the two continents. 2. Our analysis included 1003 African plots and 512 Amazonian plots. All are located in old-growth primary non-flooded forest under 900 m altitude. Tree alpha-diversity is estimated using Fisher's alpha calculated for trees with diameter at breast height >= 10 cm. Mean diversity values are lower in Africa by a factor of two. 3. Climate-diversity analyses are based on data aggregated for grid cells of 2.5 x 2.5 km. The highest Fisher's alpha values are found in Amazonian forests with no climatic analogue in our African data set. When the analysis is restricted to pixels of directly comparable climate, the mean diversity of African forests is still much lower than that in Amazonia. Only in regions of low mean annual rainfall and temperature is mean diversity in African forests comparable with, or superior to, the diversity in Amazonia. 4. The climatic variables best correlated with the tree alpha-diversity are largely different in the African and Amazonian data, or correlate with African and Amazonian diversity in opposite directions. 5. These differences in the relationship between local/landscape-scale alpha-diversity and climate variables between the two continents point to the possible significance of an array of factors including: macro-scale climate differences between the two regions, overall size of the respective species pools, past climate variation, other forms of long-term and short-term environmental variation, and edaphics. We speculate that the lower alpha-diversity of African lowland rain forests reported here may be in part a function of the smaller regional species pool of tree species adapted to warm, wet conditions. 6. Our results point to the importance of controlling for variation in plot size and for gross differences in regional climates when undertaking comparative analyses between regions of how local diversity of forest varies in relation to other putative controlling factors.